View Full Version : Revving it at standstill.
Bike is great and bulletproof in the normal way, but
Whenever it has been left for a few weeks and is cold, if you rev it even a bit, from a crawl, it cuts out.
This stops after a nice long burst and also when the bike is warm, but even with fairly regular use, i.e tonight, squeeze the throttle lever to get a nice burbling grunt a few times and once that has been achieved - click/rattle and stall.
Once fully warm it is fine, and whenever this happens it is always mid throttle - i.e you twist your right hand whilst the bike is idle or at a crawl and -blip- its dead.
I know it is a minor thing as the bike is such a superstar in how it always starts and how it rides.
Weather? What causes this?
barwel1992
05-03-10, 02:45 AM
not 100% sure but it could have somthing to do with the cold and fuel been more dense so in affect floods the bike
rictus01
05-03-10, 03:26 AM
not 100% sure but it could have somthing to do with the cold and fuel been more dense so in affect floods the bike
I presume this is humor, you're not serious are you?
Cheers Mark.
I presume this is humor, you're not serious are you?
share the wealth of knowledge then mate:D!
barwel1992
05-03-10, 03:41 AM
was been serious, but i could have misread what i was quoting hence the not %100 bit, but i read somthing a long while back (when having problems with my 50) that fuel is denser when its cold and can cause bad running, aparently thats why my 50 would smoke like a chimney in the moaning and night but be fin in the day time
:confused:
rictus01
05-03-10, 03:56 AM
look up basic carb operation (idle circuit v main operation circuit) for the original posted issue, and (to point out the obvious) it's air that gets denser in the cold, making the mixture slightly lean (as opposed to denser fuel, suggesting running rich), so of the two options you could guess at; it's the opposite one.
this is basic stuff guys, if you don't know, don't guess.
Cheers Mark.
MattCollins
05-03-10, 05:30 AM
Fuel density does not remain constant across a temperature range. Fuel distributors in this part of the world measure the density of fuel when it is sold to retailers and densities from a given batch can vary by ~5% during the course of a day. A/F mixtures still go slightly lean.
However... I doubt that this is the cause of Dizee's problems. Condensation in the bowls (carbs?) or tank (first bit of "fuel" to hit the carbs will be water) caused by warm(ish) days and cool nights, state of tune, condition of the fuel (that was left sitting), carbs, valves, cylinders etc are more likely causes.
rictus01
05-03-10, 05:48 AM
Fuel density does not remain constant across a temperature range. Fuel distributors in this part of the world measure the density of fuel when it is sold to retailers and densities from a given batch can vary by ~5% during the course of a day. A/F mixtures still go slightly lean.
However... I doubt that this is the cause of Dizee's problems. Condensation in the bowls (carbs?) or tank (first bit of "fuel" to hit the carbs will be water) caused by warm(ish) days and cool nights, state of tune, condition of the fuel (that was left sitting), carbs, valves, cylinders etc are more likely causes.
I fully agree to your first point "over a large enough temp range", however for the purposes of the scenario posed "fuel density" is totally misleading and more of no relevance; air density on the other hand does change fuel mixture by a greater margin but we aren't in the arctic or equator, and I doubt it's the cause of the OP problem, merely pointing out the guess by the follow up post, was just that a guess.
The OP has an issue coming of the idle jet onto the main,as the idle circuit is basically fixed and working fine; for any systematic diagnostician this would suggest first making sure everything was clean and balanced on the main circuit, before looking for kryptonite in the flux capacitor ......:lol:
As said it's REALLY BASIC stuff, come on you keyboard experts have google and everything......
Cheers Mark.
MattCollins
05-03-10, 06:26 AM
PS. I was agreeing with you, but being just a shade pedantic. :)
Red Herring
05-03-10, 06:45 AM
Sometimes when a bike is left the fuel left in the float bowls can dry out and gum up the jets, although this is far more common with 2 strokes that fours.
I've never had an SV carb apart before (I'm assuming it's a carb model) but on some carbs the pilot jets are really prone to this and it's the pilot jet that has the biggest impact on initial throttle openings. Once you run the bike for a while the jet gets flushed through a bit and it clears. Alternatively as has already been suggested it could just be that the fuel in the carbs goes stale and once replaced it runs better, but I'd have thought the fuel in the tank would be just as bad?
Finally it might even just be operator error. Most carb engines won't take a big throttle opening when cold, why not let it warm up a bit before blipping it?
rictus01
05-03-10, 06:53 AM
not a problem on one fitted with an accelerator pump though.
Red Herring
05-03-10, 07:08 AM
not a problem on one fitted with an accelerator pump though.
Does a 600 Hornet have an accelerator pump (or four)? My Hornet has done exactly what the Op describes from new, just let it idle for 20-30 seconds and then give it little stabs before riding it away.
Spanner Man
05-03-10, 07:22 AM
Good morning all.
Now for my fourpence worth!:D
It's all a question of throttle response Darlings. The fewer the cylinders an engine has, the longer it takes to respond to a fistful. This is because it's 'bangs' are further apart, than on an engine with more cylinders. Hence it takes longer (in fractions of a second) to overcome the inertia of the engines internals.
If an engine is not fully warmed up, the percentage of un burnt fuel per firing stroke is greater. Therefore giving it a fistful when it's cold or semi warm, effectively gives the spark plugs a bit of a soaking. This is commonly referred to as bogging down.
Cheers.
P.S. It's not a good idea to rev the B@LL@cks of an engine that's not under load in any case, & doing it when the engine is cold will accelerate engine wear further.
Alpinestarhero
05-03-10, 07:45 AM
Barwell, good idea, and technically yea the fuel is cold so its more dense. But I suspect what is really happening here is that, whilst the machine is cold (I assume the OP has a curvy :D) then when he blips the throttle, he;s getting a little carb icing, which is causing a lack of fuel flow to the engine and the bike cutting out.
Used to happen to me with my curvy, until I started using shell V-power during the cold months (perhaps you can try this aswell)
Barwell, you might have got confused with denser air when its cold? This would lean out an air/fuel mixture. My dad used to love riding his old carby GSXR750 on cool summer nights because it went a little faster and was more responsive off thr throttle :D
(i've never noticed a differance :lol:)
Peace to all
Matt
Thx for replies, its not causing an issue but is just something I noticed, onc eout and running it is faultless. It has been left standing for long periods of time this winter outside. (Yet undercover).
Alpinestarhero
05-03-10, 12:55 PM
Thx for replies, its not causing an issue but is just something I noticed, onc eout and running it is faultless. It has been left standing for long periods of time this winter outside. (Yet undercover).
That dosn't help too much either. When I;ve left my bike standing for long periods outside, its a bit of a pain to get started
Most carb engines won't take a big throttle opening when cold, why not let it warm up a bit before blipping it?
Does this explain why my er6 sometimes cuts out in the mornings when the revs are low or I'm trying to blip it? More so when the bike has not been ridden for a bit.
Dizzee, I've never heard of this happening to an FI bike like yours before :smt102
suzsv650
05-03-10, 04:00 PM
was been serious, but i could have misread what i was quoting hence the not %100 bit, but i read somthing a long while back (when having problems with my 50) that fuel is denser when its cold and can cause bad running, aparently thats why my 50 would smoke like a chimney in the moaning and night but be fin in the day time
:confused:
Thats cus it was a two stroke, they need to warm up.
fastdruid
05-03-10, 04:14 PM
P.S. It's not a good idea to rev the B@LL@cks of an engine that's not under load in any case, & doing it when the engine is cold will accelerate engine wear further.
Agreed, its also not a good idea to let it idle either...
Idle is just about the worst possible for cam loading and oil flow. There is a sweet spot for warming up it depends on the bike but for example HRC say to warm up the NC30/35 at 5-6 k as this gives the least cam loading without reving it too high.
Druid
Geodude
05-03-10, 04:26 PM
Good morning all.
Now for my fourpence worth!:D
It's all a question of throttle response Darlings. The fewer the cylinders an engine has, the longer it takes to respond to a fistful. This is because it's 'bangs' are further apart, than on an engine with more cylinders. Hence it takes longer (in fractions of a second) to overcome the inertia of the engines internals.
If an engine is not fully warmed up, the percentage of un burnt fuel per firing stroke is greater. Therefore giving it a fistful when it's cold or semi warm, effectively gives the spark plugs a bit of a soaking. This is commonly referred to as bogging down.
Cheers.
P.S. It's not a good idea to rev the B@LL@cks of an engine that's not under load in any case, & doing it when the engine is cold will accelerate engine wear further.
Yet another question of mine answered cheers :D
Spanner Man
05-03-10, 05:07 PM
Agreed, its also not a good idea to let it idle either...
Idle is just about the worst possible for cam loading and oil flow. There is a sweet spot for warming up it depends on the bike but for example HRC say to warm up the NC30/35 at 5-6 k as this gives the least cam loading without reving it too high.
Druid
Couldn't have put it better myself old Boy!:D
An engine warms up more quickly when under a light load. Therefore it's better to ride it gently when cold. than to let it idle for England. & let's not forget, that for every 5 minutes of idling, a Koala dies!:D
Cheers.
P.S. A pleasure geodude!:D
carternd
06-03-10, 11:37 AM
Couldn't have put it better myself old Boy!:D
An engine warms up more quickly when under a light load. Therefore it's better to ride it gently when cold. than to let it idle for England. & let's not forget, that for every 5 minutes of idling, a Koala dies!:D
Cheers.
P.S. A pleasure geodude!:D
Hurray! I don't have to stand about warming the bike up. Best news I've had all year. Just keep the revs down for the first couple of miles. Why the hell don't they tell you this in the manual?
Alpinestarhero
06-03-10, 03:22 PM
Bit of a side-track here but still on topic, to do with warming up engines sort of
Being a honda V4 geekazoid (but not as much as fastdruid, and probably still not as much as spannerman) I read the honda V4 book written by julian ryder in one sitting, and Mr Ryder recalls the story of early honda VF's having incured major engine faliure, as a result of excessive camshaft wear. Honda never came across this in their testing, since it was reported that the test riders would warm their engines up "properly"...Mr Ryder dosn;t state what this means, but I assume it means allowing the bike to reach is optimum running tempurature (85 deg.C or so?) before setting off. Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated. There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles; a typical owner started his/her bike on choke, probably let it run at a fast idle for about 20 seconds beore knocking it off and going for their ride. I suppose with these cold parts, the tolerances where even much worse than when warm and further accelerated the wear.
Something else I remember from that book; honda engineers would fill the bikes up with oil, and let the testers go out and ride them. They'd only change the oil 20,000 miles later.
MattCollins
06-03-10, 04:37 PM
... Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated. There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles ....
That sounds a bit weird. Is that right? I am not sure what they're doing these days, but I come from a time when bearing caps /top cover were always mated as a machined set to the head. ie caps are bolted in position prior to boring of camshaft tunnel and are not interchangeable between heads.
Alpinestarhero
06-03-10, 05:34 PM
That sounds a bit weird. Is that right? I am not sure what they're doing these days, but I come from a time when bearing caps /top cover were always mated as a machined set to the head. ie caps are bolted in position prior to boring of camshaft tunnel and are not interchangeable between heads.
Well, that was the point; honda started doing it differantly, i don't know why...maybe it was easier / quicker? Either way, it ended up costing them dearly and they went back to doing it the proper way. One of those things where honda got over-confident (read: cocky)
fastdruid
06-03-10, 05:43 PM
Apparently, the problem was due to the camshaft bearings...I don;t know the technical terms so someone will have to help me out here, but the part you bolt down ontop of the camshaft was made in a completly differant place to the bottom part, so the two parts where never perfeclty (as much as perfect can get on a mass-produced head) mated.
Most are line bored, ie you bolt everthing together, then bore (ie drill) it through in one sweep, ensures that everything is inline. The VF750 apparently had too small holders, the VF500 had larger ones and didn't suffer as much.
There was enough free play / clearance that the cam shafts would move around and pretty much wear themselves out after a few thousand miles; a typical owner started his/her bike on choke, probably let it run at a fast idle for about 20 seconds beore knocking it off and going for their ride. I suppose with these cold parts, the tolerances where even much worse than when warm and further accelerated the wear.
IIRC the problem was a multiple one, not that simple but was essentially up to 6 things in combination.
1) Forked followers - they tilt when adjusting valve clearances (fix was to use two feeler gauges)
2) variation in cam to bearing clearances - needs a special tool to hold the camshaft[1]
3) Poor camchain tensioner
4) Soft cams
5) Heat - the V4 gets very very hot, rear cams apparently go first.
6) Poor lubrication.
Druid
[1] To combat this, Honda developed a special tool to hold the cam in place. Any bike shop tuning a V4 had better have this tool. It doesn't cost much ($15) and isn't hard to use. Get one; even though it doesn't completely solve the problem, it is a requirement. Part number is 07979-MK30000, name is "V4 tappet adjust". The service bulletin issued with this tool recommends valve clearance of .006 inches instead of .005 that the Sabre/Magna originally specified, as well as use of premium motorcycle oil, changed frequently, and avoidance of prolonged idling.
Biker Biggles
06-03-10, 05:45 PM
I thought it was just a metalurgy issue with poor quality metals or poor case hardening?????
The issue with cam caps sounds a bit like a problem they had with the CBR600 about 98/99 when there was an issue with the caps not quite seating properly after valve clearence checks.Or is my memory playing up with age???
Alpinestarhero
06-03-10, 05:47 PM
3) Poor camchain tensioner
but thats a honda characteristic anyway :lol:
Thankyou for the extra information there Cheif V4
fastdruid
06-03-10, 05:50 PM
but thats a honda characteristic anyway :lol:
Eh? I have 4 honda's in my garage and not a single camchain tensioner between them. ;) For that matter not a single camchain between them. :lol:
Druid
Alpinestarhero
06-03-10, 05:53 PM
Eh? I have 4 honda's in my garage and not a single camchain tensioner between them. ;) For that matter not a single camchain between them. :lol:
Druid
lol you know what I mean...buy a honda that dosnt have gear-driven cams (soooooo pre-vtec V4's and SP1/SP2) and you better cross your fingers and carry a lucky horseshoe for that CCT :lol:
It is a long running joke in the Spannerman workshop that the VFR750's / pre VTEC 800's had the most reliable CCT's honda ever made
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